The present invention relates to an apparatus for forming a container which is of the type presented in the preamble to the attached claim 1.
It is known to a person skilled in the art to form from liquid packaging board cylindrical containers which comprise a vertical cylindrical casing formed by joining together the opposite sidewall margins of the blank with heat-sealable coating, and end members closing the sidewall blank at the top and bottom, the upper end member having an opening closed, for example, with a closure cap or a closing flap. Containers of the type described above are used in packaging different beverages in a sterile and airtight manner.
The container into which the material to be conserved, for example a beverage, is fed later, is formed automatically in a container-forming unit in which there is a set of so called wrapping mandrels around which the casing is formed by wrapping. The wrapping mandrels are placed in a rotating structure, which moves the mandrels between different processing stations. At each station one operation is carried out at a time, and thus a can-shaped casing is gradually formed, then removed from the mandrel at the last processing station and conveyed to a filling unit for filling and closing.
The apparatus described above is known in the prior art, and described for instance in European patents EP-B1-0 038 488 and EP-B1-0 018 470. The solutions presented in the said patents are characterised especially in that the blank is wrapped around the mandrel by using a mechanical pressing means which presses one end of the blank against the outer side surface of the mandrel and moves with the rotating movement of the mandrel, which pulls the blank around the mandrel and forms a closed structure, after which the side sealing is performed. In the patent EP-B1-0 018 470 there is also presented a particular securing member device, which ensures that the blank remains against the outer surface of the mandrel during the rotational movement of the mandrel. The wrapping phase described above requires many moving mechanical parts, in addition to which the mandrel must be arranged to be rotating.
The objective of the present invention is to eliminate the disadvantages described above and to present an apparatus in which the wrapping phase can be made simpler with at least the same reliability of operation, in addition to which the structure of the apparatus for forming a container is simplified. To achieve this, the container-forming apparatus in accordance with the invention is mainly characterised in that which is presented in the characterising part of the attached claim 1.
The container-forming apparatus is characterised in that the outer surface of the wrapping mandrel has suction openings around the whole perimeter of the mandrel, and these suction openings are connected to a source of underpressure in order to pull the blank around the mandrel. This means that mechanical means are not needed for wrapping except if needed, as auxiliary means, and in addition to this the mandrel can be arranged so as to be non-rotating in the structure holding and moving the mandrel, i.e. no additional transmission is needed in the container-forming apparatus for the rotational movement. With the aid of the suction, the wrapping tension can also be adjusted, allowing for the rigidity of the blank.
A vertical row of suction openings at one specific point on the perimeter of the mandrel is presented in the publication EP-B1-0 038 488 mentioned above. These suction openings do not cause the wrapping of the blank around the mandrel and they are not directly in contact with the inner surface of the blank, because they are designed only for positioning the separate strip functioning as an aid to sealing before the actual mechanical wrapping.
As regards the other advantageous embodiments of the present invention, reference is made to the dependent claims attached and to the explanations described later.